Formation of adrenaline in the iris-ciliary body from adrenalone diesters

Many diesters of adrenalone have high ocular sympathomimetic activity although adrenalone itself, even if delivered intraocularly, is practically inactive. Thus these diesters cannot be considered pro-drugs of adrenalone, since adrenalone is not a drug. The mechanism of action of these adrenalone derivatives was studied on the selected, potent diisovaleryl adrenalone. It was found that adrenaline is formed from the diester, but not from adrenalone. While the inactive adrenalone is also formed hydrolytically and found in every compartment of the eye, the active epinephrine (adrenaline) was found only in the iris-ciliary body, as a result of a reduction-hydrolytic steps sequence. Thus the adrenalone diesters represent a type of site-specific delivery system for epinephrine.